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The Celebes Medaka, sold under the name Oryzias celebensis/latipes, belongs to the ricefish group, a collection of small, active and peaceful surface-dwelling fishes. The trade name sometimes combines Oryzias celebensis and Oryzias latipes, two related species with different natural ranges. The Sulawesi form is especially appealing because of its understated appearance, egg-carrying reproduction and good adaptation to a mature aquarium. This wild-collected fish is less common than the standard Japanese medaka. It suits aquarists able to provide stable water, a covered aquarium and a group of compatible fish.

General species description

Oryzias celebensis/latipes is a small, streamlined surface fish adapted to calm or slow-moving water. Like other Oryzias, it often remains within the upper few centimetres of the aquarium and readily uses areas shaded by floating plants. Its temperament is generally peaceful and social, making group maintenance preferable to keeping a single fish. It is a substrate spawner: the eggs are fertilized and temporarily remain attached to the female before being deposited among vegetation. The Sulawesi form has moderate interest in the aquarium hobby and is less commonly available than Japanese medaka. The rarity rating used here is therefore 2 out of 3, or uncommon.

Geographical origin and biotope

Country of reference: Indonesia. Oryzias celebensis comes from Sulawesi, formerly known as Celebes, while Oryzias latipes is native to East Asia. For the Celebes Medaka, an aquarium should suggest the shallow freshwater habitats of Sulawesi: stream margins, ditches, connected pools and slow sections of small waterways. The water is generally clear to lightly tinted, with limited turbulence and light filtered by vegetation. In captivity, this tropical origin calls for a stable temperature without a pronounced cool season, as well as a secure cover because these fish may jump when startled.

Precise location and local name

The main geographical reference is Sulawesi, Indonesia, particularly the island’s freshwater habitats associated with the form called Oryzias celebensis. The most widely understood trade name is medaka, a Japanese term mainly used for Oryzias latipes. In the aquarium trade, Celebes Medaka helps distinguish the Sulawesi form from the Japanese medaka. The commercial name Oryzias celebensis/latipes may therefore cover two taxonomic references; keeping the geographic origin and strain separate in breeding records is advisable. This helps prevent mixing fish from Sulawesi with domesticated Japanese medaka lines.

Appearance and physical characteristics

The body is small, fusiform and slightly laterally compressed, with a mouth adapted to feeding at the surface. The base colour ranges from silvery grey to olive brown, with reflections that vary according to lighting, age and breeding condition. The fins are transparent to lightly tinted; in males, they may appear more developed and more strongly contrasted. Females are usually deeper-bodied when carrying eggs. The slender profile, dorsally positioned eyes and surface-oriented swimming are useful features when identifying a ricefish. Adult size remains modest, allowing a group to be kept in a relatively compact aquarium, provided sufficient swimming length and a secure cover are supplied.

General diet

In the wild, Oryzias celebensis/latipes mainly takes small prey found near the surface, including insects, larvae, microcrustaceans and other planktonic organisms. In an aquarium, it accepts fine dry foods, but its diet should regularly include small frozen or live foods. Baby brine shrimp, daphnia and cyclops are suitable for adults and can encourage spawning. Fry require very fine foods, such as microorganisms or a quality powdered food. Feed small portions frequently, since the mouth is small and floating leftovers can quickly affect water quality. A varied diet supports colour, vitality and egg production.

Essential data

• Name of the source river: small streams and lentic habitats of Sulawesi
• Local name used: medaka; ikan medaka in the Indonesian aquarium trade
• Origin of the scientific name: Oryzias identifies the ricefish genus; celebensis refers to Celebes, the former name of Sulawesi; latipes is the related Japanese species
• Etymology of the complete name: Oryzias, linked to rice; celebensis, from Celebes; latipes, from the Latin latus, broad, and pes, foot
• Common or vernacular names: Celebes Medaka, Sulawesi ricefish, medaka
• Family: Adrianichthyidae
• Subfamily: Oryziinae
• Name pronunciation: oh-RIZ-ee-ass seh-leh-BEN-siss / oh-RIZ-ee-ass lah-TEE-pess
• Discovery: Oryzias latipes, Coenraad Jacob Temminck and Hermann Schlegel, 1846; Oryzias celebensis, Maurice Kottelat, 1990
• Maximum adult size: about 4 cm
• Water temperature and pH: 23 to 28 °C; pH 7.0 to 8.0
• Stream appearance and surrounding vegetation: calm or slow water, shallow margins, with submerged, emergent and floating plants
• Typical tankmates: local small ricefish, suitable freshwater shrimp, peaceful snails and other small non-predatory surface fish
• Temperament and behaviour: peaceful, active, social and mainly surface-oriented
• Water depth: shallow to moderate, often in shallow marginal areas
• Sexual dimorphism: males are usually slimmer with more developed fins; females become rounder when carrying eggs
• Bottom structure and flow: mud, sand or small plant debris; low to moderate current

In your aquarium

Success begins with a mature, well-covered aquarium planted to create calm areas near the surface. Keep Oryzias celebensis/latipes in a group, with gentle filtration and clean water that is neutral to slightly alkaline. Fine, varied food, including live or frozen items, supports adult condition and spawning. Because this form is wild-collected and less common, preserving its provenance, avoiding hybridization with other strains and never releasing surplus fish outdoors are responsible practices. Stable conditions, gentle flow and a secure lid are the main keys to long-term success with this interesting ricefish.